The present invention relates to a method for detecting the coordinate position for the grinding point of a grinding wheel in a grinding machine with a swiveling table and the related device thereof.
An example of a conventional grinding machine having a swiveling table is described hereinafter with reference to FIG. 12.
Workpiece [W] is supported by a spindle head (not shown in the drawing) which is arranged on a table (not shown in the drawing) and rotatably driven about an axis parallel to the Z-axis which is the travel direction of the aforesaid table. A wheel head comprises a feed table (not shown in the drawing) that is movable in the X-axis direction perpendicular to the Z-axis direction, and a swiveling table 13 mounted on the feed table to be turned about a vertical axis relative to the aforesaid feed table. The swiveling table 13 supports an external grinding wheel Ga through a wheel spindle 22 which is rotated about an horizontal axis. Swiveling table 13 is drivably turned by a numerically controlled (NC) servomotor not shown in the drawing.
For example, in the setup operation for taper grinding, swiveling table 13 is rotated counterclockwise only through a taper angle .theta..sub.G extending from a reference position wherein the rotational axis of external grinding wheel Ga is parallel to the Z-axis, as indicated by the solid line in the drawing, to a set position indicated by the broken line in the drawing. At this time, the grinding point of external grinding wheel Ga travels a distance Z.sub.0 in the Z-axis direction and a distance X.sub.0 in the X-axis direction to arrive at point A.sub.0.
Accordingly, when the distance between the center of swiveling table 13 and the grinding point of grinding wheel Ga is designated R.sub.G, the displacements of Z.sub.0 and X.sub.0 are calculated based on the aforesaid distance R.sub.G and the turning angle .theta..sub.G of swiveling table Ga, so as to make the necessary positional corrections for said table and grinding wheel. Thus, the aforesaid data R.sub.G and .theta..sub.G expressing the position of the grinding wheel point must be calculated by some method and must be previously stored in memory, as parameters.
The values or R.sub.G and .theta..sub.G expressing the position of the grinding point of external grinding wheel Ga can be obtained from the blueprint of the grinding machine. Inasmuch as the actual position and theoretical position of the grinding point of external grinding wheel Ga may differ due to machining errors or assembly errors during assembly of the machine, it is difficult to precisely measure the actual position of said grinding point.